1. Field of the Invention
The present invention relates to a control unit for a turbocharged internal combustion engine.
2. Description of the Related Art
For example, Japanese Patent Application Publication No. 10-89106 (JP-A-10-89106) describes an internal combustion engine that is equipped with a turbocharger (independent exhaust engine). The internal combustion engine described in JP-A-10-89106 includes: a first exhaust valve that opens and closes a first exhaust passage that is communicated with a turbine; and a second exhaust valve that opens and closes a second exhaust passage that bypasses the turbine. In the described internal combustion engine, exhaust energy may be directed to the turbine by opening the first exhaust valve. In addition, exhaust gas may be discharged to bypass the turbine by opening the second exhaust valve; therefore, it is possible to reduce pumping loss that is caused by the exhaust gas.
If there is a valve overlap period is between an opening period of an intake valve and an opening period of an exhaust valve in the internal combustion engine equipped with a turbocharger, this may cause air and fuel to flow from the intake side to the exhaust side through the combustion chamber under high load if the compressed pressure is higher than back pressure. JP-A-10-89106 does not describe an air-fuel ratio control when flowing of the air and fuel occurs.